1. Field of the Invention
This invention relates to fluid-level sensing devices used to shut off a fluid-producing system in response to rising fluid levels caused by the system that result in a risk of fluid overflow and/or damage to surroundings, specifically to a fluid-level sensing device that is typically connected to the perimeter wall of a fluid collection pan or tray associated with a fluid-producing unit, such as an air conditioning or furnace unit, and is often mounted to, with, or near a drain line connection or drain line connection assembly where it is positioned for float body deployment when rising fluid exceeds a threshold level considered safe. Hereinafter, for simplicity of description alone, the word “pan” will be used to identify a fluid-collecting device used in association with the present invention, without any intent of limitation. The present invention employs the interaction of two magnets to close a circuit in a micro switch and thereby send a shut-off signal to the fluid-producing system to stop its fluid production so that accumulated fluid in the pan monitored by the present invention fluid-level sensing device does not exceed a pre-determined level considered safe. The first magnet is attached to the distal end of an external micro switch arm and the second magnet is positioned within the distal end of a pivoting float body that vertically deploys in response to rising fluid. A single housing with two separate vertically stacked chambers (hereinafter identified as the “upper chamber” and the “lower chamber”) is used to isolate the encapsulated switch in a position directly above the float body, with the magnetic forces between the upper and lower magnets interacting through the central housing wall between them, as well as through the float body's upper surface, the bottom of any magnet-holding cup attached to micro switch external arm, and any other materials used to position and/or retain the two magnets in their usable positions. After float body deployment, manual reset of the float body to its pre-deployment position is accomplished via its lever-like distal end that extends beyond the vertically-extending outer wall of the float/switch housing. Attraction or repulsion forces between the two magnets can be the triggering factor for circuit closure, but repulsion is preferred. The lower open-bottomed chamber in the housing below the micro switch is substantially filled by the buoyant float body. There is no opening through the housing's central wall to allow for communication between the lower open-bottomed float body chamber and the upper open-topped micro switch chamber. Further, the main body of the micro switch is completely encapsulated in waterproof material to protect it from corrosion and ensure reliable and long-term repeat performance. Electrical wiring extending in an upwardly direction from the micro switch connects it to the fluid-producing system for which monitoring is required, so that when the fluid level in a pan to which the present invention is attached exceeds a pre-determined threshold level considered safe, the rising fluid causes the distal end of the float body to pivot in an upwardly direction and increase magnetic interaction between the magnet it supports and the second magnet associated with the distal end of the micro switch arm, which when the threshold level is reached causes a circuit to be closed and results in an electric signal being sent to the fluid-producing system to shut it off and prevent overflow damage to the system, surrounding equipment, nearby objects, and/or adjacent materials. It is also preferred for the lower chamber of the float/switch housing to have one or more air vents that prevent airlock malfunction of the float body. However, in combination or in the alternative, the slot used to guide the lever-like distal end of the float body during its vertical deployment can be configured to serve as an effective air vent. It can also be narrow to avoid the entrance of debris and other non-fluid materials (such as algae or mold) that could interfere with effective and reliable float body performance.
Alternative ways for quick mounting of the present invention housing to a fluid-collecting pan are contemplated, including the use of a quick-mounting shelf area pre-molded into the pan that is configured to facilitate and expedite a drain line connection and placement of the float switch into a level orientation for most reliable long-term operation. Thus, when the present invention float/switch housing is permanently or temporarily associated with a mounting plate having a configuration complementary to that of a shelf area pre-molded into the pan, the act of drain line connection using the shelf-area provides immediate leveling of the float switch body relative to the pan, so that once leveling of the pan is achieved the resulting float deployment trouble-free, reliable, and reproducible without malfunction for long-term use. The lever-like distal end of the float body provides an easy test point for an installer to be certain that float body deployment occurs at the proper fluid level, typically in as little water accumulation as possible. At least one example of the manner in which threshold fluid level adjustment can be accomplished is presented later in this invention disclosure. Applications of the present invention include, but are not limited to, use in air conditioning and furnace condensate collection/overflow prevention applications for shutting off an air conditioning or furnace system when condensate collected in a pan beneath the portion of the system creates a water damage risk by exceeding a pre-established threshold amount, as well as other applications including where rising condensate/fluid beyond a safe threshold limit is undesirable and automated shut-off of the condensate/fluid source is needed or desired to eliminate back-up damage to the condensate producing system or the risk of damage to surrounding objects and structures.
2. Description of the Related Art
When condensates from air conditioning and furnace systems, as well as other condensates, are collected in a pan or tray to avoid contact with surrounding objects and structure, a risk of overflow and/or back-up into the system producing it remains. As a result, fluid-level sensing devices have been employed with collection pans and trays to shut-off the source of condensate flow when the amount of condensate collected exceeds a predetermined threshold level considered safe. However, prior art float switches have many disadvantages, including insubstantial float body shape or construction that reduces buoyancy, switching components having materials or construction with insufficient corrosion resistance, float body positioning that presents a risk of debris interference, float body positioning that presents substantial exposure to collected fluid and a risk of interference from mold and algae growth, float bodies subject to airlock malfunction, float bodies that require the collection of a substantial amount of fluid before their deployment occurs, and/or float bodies not substantially filling the associated float housing wherein prompt float body deployment is sometimes delayed or prevented by its tendency to wobble. Further, installation time of prior art devices can be lengthy when there is guess-work needed by an installer for selecting, mounting, leveling, and otherwise adjusting an appropriately matching and adjusting a float switch and condensate collection pan for correct operation in an intended application, particularly when a hole needs to be drilled in a pan. In addition, maintenance is often required after installation of prior art fluid-level sensing devices to ensure continued stable, reliable, and reproducible float body deployment for electrical shut-off of a fluid-producing unit or system when the accumulated fluid being monitored by the float switch rises beyond a threshold level considered safe. Further, air conditioning condensate collection pans are typically installed in hot attics, and other places where significant temperature fluctuations can occur, and many prior art plastic condensate collection pans have insufficient construction whereby a float switch mounted on the upper edge of the pan's perimeter wall will lean in over a period of time and no longer be maintained in the needed vertical orientation for a prompt and reliable deployment in response to excessive condensate collection in the pan.
The present invention's use of a pivoting buoyant float body in combination with two magnets overcomes deficiencies in the prior art. First, the pivoting float body of the present invention does not have a tendency to wobble, as does a freely-floating body whose vertical movement is guided by a concentric tube or rod inserted centrally through it. Second, the present invention magnets provide rapid circuit closure once the float body begins to deploy, so that a shut-off signal to halt fluid production can be sent with less collected fluid. Third, venting of the present invention float housing substantially reduces airlock formation and since its float body substantially fills the float housing chamber within which it is positioned, interference from debris is minimal. In addition, when the present invention fluid-level sensing device is in fixed association with a drain line connection having a mounting plate, mating it with a complementary configured quick-mounting shelf area in a fluid-collecting pan creates a fast and easy drain line connection, wherein switch installation is accomplished simply as a consequence of the drain line connection being made and the act of drain line connection provides immediate leveling of the float switch relative to the pan, so that once the relatively easy step of leveling the pan is achieved the resulting vertical float body deployment trouble-free, reliable, and reproducible without malfunction during long-term use. Another advantage provided by the present invention fluid-level sensing device over the known prior art is the lever-like distal end of its float body which provides an easily manipulated finger latch to allow post-installation testing by the installer to be certain the present invention fluid-level sensing device is operational and functioning according to need. When a pan with a quick-mounting shelf area is used (particularly one generally trapezoidal in configuration), attachment of the mounting plate to the shelf area also provides a substantial connection that is sturdy and not subject to changes in orientation over time that often occur as a result of sagging or lean in of prior art condensate tray or pan walls. In addition, the present invention sensing device has a sturdy/rugged design and sturdy corrosion-resistant construction. Also, since the lower chamber of the present invention float/switch housing has an open bottom configured to allow condensate collected therein to easily drain once fluid levels subside, its float body is not routinely in contact with collected condensate. Thus, the float body is less likely to become clogged with mold, algae, and/or debris, further protecting it from malfunction.
The closest inventions to the present invention appear to be those disclosed in U.S. Pat. No. 6,140,925 to Lee (2000) and U.S. Pat. No. 6,339,985 to Whitney (2002). The Whitney invention discloses a coffee maker having closure between two chambers achieved by magnetic action, with one of its magnets on the distal end of a pivoting arm. In contrast, the Lee invention discloses a magnetically operated float switch having a float body that is vertically deployable on a central rod, with the rod having a top magnet positioned below a micro switch. However, neither the Lee nor the Whitney inventions disclose a unitary housing with separate isolated vertically-stacked chambers with an open-topped upper chamber configured for holding a corrosion-resistant encapsulated micro switch above a pivoting float body in the open-bottomed lower chamber. Also, the provisions for post-installation testing, quick mounting to a condensate pan, and reducing interference to the float body by mold, algae, and/or debris, which are important to the present invention, are not discussed in the Lee and Whitney disclosures. No other apparatus is known that has the same structure, functions in the same manner, or provides all of the advantages of the present invention.